1. Field of the Invention
The present invention relates to a resin-sealed semiconductor device, and particularly to a resin-sealed semiconductor device which is easy to handle and has a package structure with high reliability.
2. Description of Related Art
FIG. 11 is a partially broken-away perspective view showing a conventional resin-sealed semiconductor device 1a. In the drawing , a semiconductor element 1 having a integrated circuit or the like formed on the surface of a semiconductor wafer such as silicon or the like is mounted on a substrate 2 and secured thereto by an adhesive layer 3. Electrodes (not shown) on the semiconductor element 1 are connected to inner leads 6 by bonding wires 7. The semiconductor element 1 and the inner leads 6 are covered with a sealing resin 4, while outer leads 5 connected to the inner leads 6 project to outside of the sealing resin 4.
In the conventional resin-sealed semiconductor device 1a configured as described above, the semiconductor element 1 is connected to the outer leads 5 through the bonding wires 7 and the inner leads 6 so that electrical signals are input and output through the outer leads 5 when the semiconductor device 1a is used.
In the above resin-sealed semiconductor device 1a, the inner leads 6 must be connected to the semiconductor element 1. There is thus the need for some distance between the semiconductor element 1 and each of the inner leads 6 from the viewpoint of the characteristics of metal wires such as a gold (Au), copper (Cu), aluminum (Al) wire or the like, which is used as the bonding wires 7. In addition, the length of each of the inner leads 6 must be secured for preventing the outer leads 5 and the inner leads 6 from slipping off the sealing resin 4 during forming (bending) of the outer leads 5. The size of the resin-sealed semiconductor device 1a is thus significantly increased, as compared with that of the semiconductor element 1. The conventional semiconductor device thus has the problem that it is difficult to reduce the size, weight and thickness thereof.
On the other hand, mounting a semiconductor element by the flip chip method, as shown in FIG. 12, has the possibility that the semiconductor element 1 is damaged during mounting because a bare chip, i.e., the semiconductor element 1, is handled to place it on a substrate 11 for mounting. The method also requires the step of covering the whole element with a potting resin (not shown) or the like after the electrodes 8 of the semiconductor element 1 are mounted on lands 9 of the substrate 11, with bumps 10 therebetween. The method thus has the problem that the resin sealing work is further required before or after the usual reflowing step.
The conventional bumps 10 also have the problems that it is difficult to make the height uniform and voids easily occur in the bumps 10, that the bumps 10 are easily damaged due to their low strength because they are made of solder, gold or the like. There is the great possibility that the bumps 10 will become separated after mounting on the substrate because the bumps 10 have low shear strength.